Knowledge-based driver apparatus for high lumen maintenance and end-of-life adaptation

Abstract

A knowledge-based driver is provided for powering a solid-state light source with a constant current, including a memory that stores lumens per amp and volts per amp performance characterizations of the light source over time, and a controller that operates in a test mode to estimate the light source degradation based on voltage feedback obtained at a predetermined test current value, and to adjust the drive current in normal operating mode according to the estimated device degradation to implement constant lumens control without external optical feedback components.

1. A driver apparatus for powering a solid-state light source, the driver apparatus comprising:
 a constant current power source with an input to receive input electrical power and an output coupleable to a solid-state light source, the output operative to provide electrical output current to drive the at least one solid-state light source; 
 a memory storing a lumens per amp performance characterization of the solid-state light source over time as well as a volts per amp performance characterization of the solid-state light source over time; and 
 a controller operatively coupled with the memory and with the power source to receive at least one feedback value from the power source and to provide a current setpoint signal or value to the power source; 
 the controller being operative in a normal mode to provide an operating current setpoint value or signal to cause the power source to drive the solid-state light source at a corresponding output current level; and 
 the controller being operative in a test mode:
 to provide a test mode current setpoint value or signal to cause the power source to drive the solid-state light source at a corresponding predetermined test current level, 
 to receive a voltage feedback value from the power source while the power source is driving the solid-state light source at the test current level, 
 to determine an estimated degradation of the light source based at least partially on the voltage feedback value using the volts per amp performance characterization, and 
 to update the current setpoint value or signal based on the estimated degradation using the lumens per amp performance characterization. 
 
 
     
     
       2. The driver apparatus of  claim 1 , where the controller is further operative in the normal mode to receive a voltage feedback value from the power source, to detect rapid changes in the voltage feedback value, and to enter a fault mode if a rapid change is detected in the voltage feedback value, and where the controller is operative in the fault mode to implement at least one of a remedial measure to attempt to clear a detected fault condition of the light source and a notification measure to attempt to notify a user of the detected fault condition. 
     
     
       3. The driver apparatus of  claim 2 , where the controller is operative to implement a remedial measure in the fault mode by briefly overdriving the light source, and to selectively resume the normal mode operation if the fault is cleared. 
     
     
       4. The driver apparatus of  claim 2 , where the controller is operative to implement a notification measure in the fault mode by causing the power source to flash the light source to attempt to notify a user of the detected fault condition. 
     
     
       5. The driver apparatus of  claim 2 , where the memory stores the lumens per amp performance characterization and the volts per amp performance characterization of the solid-state light source over time as lookup tables, and where the controller is operative in the test mode to determine the estimated degradation of the light source based on the voltage feedback value using the volts per amp performance lookup table, and to update the current setpoint value or signal based on the estimated degradation using the lumens per amp performance lookup table. 
     
     
       6. The driver apparatus of  claim 2 , where the memory stores the lumens per amp performance characterization and the volts per amp performance characterization of the solid-state light source over time as formula parameters, and where the controller is operative in the test mode to determine the estimated degradation of the light source based on the voltage feedback value using the volts per amp performance formula parameters, and to update the current setpoint value or signal based on the estimated degradation using the lumens per amp performance formula parameters. 
     
     
       7. The driver apparatus of  claim 1 , where the memory stores the lumens per amp performance characterization and the volts per amp performance characterization of the solid-state light source over time as lookup tables, and where the controller is operative in the test mode to determine the estimated degradation of the light source based on the voltage feedback value using the volts per amp performance lookup table, and to update the current setpoint value or signal based on the estimated degradation using the lumens per amp performance lookup table. 
     
     
       8. The driver apparatus of  claim 1 , where the memory stores the lumens per amp performance characterization and the volts per amp performance characterization of the solid-state light source over time as formula parameters, and where the controller is operative in the test mode to determine the estimated degradation of the light source based on the voltage feedback value using the volts per amp performance formula parameters, and to update the current setpoint value or signal based on the estimated degradation using the lumens per amp performance formula parameters. 
     
     
       9. The driver apparatus of  claim 1 , where the controller is operative to enter the test mode periodically. 
     
     
       10. The driver apparatus of  claim 1 , where the controller is operative in the test mode to detect an end-of-life condition of the light source based at least partially on the estimated degradation of the light source and to enter an end-of-life mode if an end-of-life condition is detected, and where the controller is operative in the end-of-life mode to implement at least one of an end-of-life measure to modify control of the light source and an end-of-life notification measure to attempt to notify a user of the detected end-of-life condition. 
     
     
       11. The driver apparatus of  claim 10 , where the controller is operative to implement an end-of-life measure by overdriving the light source to attempt to provide constant lumens operation of the light source in the end-of-life mode. 
     
     
       12. The driver apparatus of  claim 10 , where the controller is operative to implement an end-of-life notification measure by causing the power source to flash the light source to attempt to notify a user of the detected end-of-life condition. 
     
     
       13. The driver apparatus of  claim 10 , where the controller is further operative in the normal mode to receive a voltage feedback value from the power source, to detect rapid changes in the voltage feedback value, and to enter a fault mode if a rapid change is detected in the voltage feedback value, and where the controller is operative in the fault mode to implement at least one of a remedial measure to attempt to clear a detected fault condition of the light source and a notification measure to attempt to notify a user of the detected fault condition. 
     
     
       14. The driver apparatus of  claim 1 , where the memory stores at least one environmental performance characterization, and where the controller is operative in the test mode to determine at least one environmental characteristic of the light source and to determine the estimated degradation of the light source based at least partially on the environmental characteristic using the environmental performance characterization.